A hernia is defined as a pathology characterised by the protrusion of organs, or their parts, from their natural position through an anomalous aperture in the human tissue. Such a pathology requires a hernioplastic surgical operation during which a reinforcement parietal prosthesis is implanted in the area of the tissue affected by the hernia in order to re-establish the continuity of the tissue and to create a resistance zone. During hernioplastic inguinal surgical operations two substantial problems arise. The first problem relates to the so called relapse or the recurrence of the hernial pathology. The second problem consists in the fact that the hernioplastic operation must not damage the spermatic cord when the reinforcement parietal prosthesis is lodged around the same.
Before carrying out hernioplastic operations, the practice had been to carry out a direct suture of the damaged tissue (Bassini-Shouldice Method). With this operations there has been a very high number (25%) of relapses. To solve this problem surgical techniques have evolved thanks to the implantation of parietal prostheses made up essentially of meshes and placed onto the damaged tissue. The parietal prostheses have helped in lowering the incidence of relapses but have not completely eliminated the problem. In fact, a relapse may be attributed to many factors including the mispositioning of the prosthesis, the fixing suture for the prostheses to the human tissue which can lead to an erroneous tension distribution and the creation of dead spaces and seromas. To solve this problem surgeons have tried to use prostheses of different materials (polypropylene monofilament has proved the most ideal for this purpose), that is, biocompatible meshes with stable physico-chemical and dimensional characteristics such as high resistance to tensile stress, stable biologically, which do not induce inflammatory reaction and which permit a rapid reaction of the fibroblasts, a high capacity to adapt to muscular movements and contractions. An important characteristic turns out to be the pattern of the mesh: in this way it is possible to have a mesh with optimum qualities so as to adapt itself perfectly to the site of the implant. Initially the pattern was made manually in the operating theatre; the next step developed by the manufacturing companies was to reproduce prostheses already preshaped with accurately finished outer edges, fraying- and breaks-free and being of different sizes. The first preshaped prostheses were sutured to the human tissue: one of the disadvantages was the transmitting of tensions between the prosthesis and the human tissue. Then new prostheses and different surgical techniques were approached such as the tension free sutureless mesh and sutureless tension-free repair: this technique requires the use of a prosthesis having a single layer preshaped mesh and provided with a hole and a longitudinal slit to permit the insertion of the spermatic cord into the hole. This prosthesis is not sutured to the human tissue because it remains confined within a well defined anatomical space which constricts movements of the same. The parts of the prosthesis adjacent to the longitudinal slit can be sutured together or left free: in the first case the wings can move and damage the spermatic cord, in the second case the formation of relapses, damage to the spermatic cord and the bending of the parts of the prosthesis along the longitudinal slit are encouraged leading to the formation of dead spaces. This solution does not rule out a possible migration and deformation of the mesh in case that said parts open out if they are free or in case they bend when connected by a suture stitch; nor does it succeed either in completely resolving the problem of the risk of damage to the spermatic cord. Moreover with this solution the risk of the incidence of relapses is not completely eliminated.
To try and solve these problems there has been produced a parietal mesh of reinforcement, subject of the international patent application WO 01/85058 under the title “Double layer anatomic surgical mesh” in the name of the same applicant: it concerns a double layer mesh made up of two superimposed layers with equal coincident holes, and radial divergent slits. The layers present respective external coincident edges joined by a continuous laser welding with the exclusion of the area where there are present the two slits that create two wings initially overlapping, the function of which is to block the mesh at the spermatic cord, avoiding damaging it and without using surgical stitches between the wings. This prosthesis has been designed to be used in those surgical operations where a posterior approach is envisaged: that is the prosthesis is placed in contact with the internal face of the human tissue. Even though this prosthesis has shown itself to be particularly effective from either the point of view of implantation or from that of relapses, it does have the drawback of being particularly expensive due to the high use of materials and of skilled labour and, for this reason, it is not used for more common surgical operation where anterior access is envisaged.